COMMUNICATION SYSTEM OF SATELLITE MULTIPLE ACCESS WITH DIVISION OF CODIGOMULTIPLEJADO WITH DIVISION PE TIME, IN PACKAGES FIELD OF THE INVENTION This invention relates to satellite communication systems and in particular to said system using a combination of on-board packet switching, uplink CDM? in packet (ie multiple access with code division) and TDM downlink transmission (ie, split with time division). BACKGROUND OF THE INVENTION Communication access schemes using satellite connections are commonly accomplished by FMDA processing techniques (ie multiple access with frequency division) and TDMA (ie multiple access with time division). Often, the uplink signal is transmitted to the destination by the satellite using bent tube techniques, meaning that the satellite simply acts as a repeater without performing any on-board switching or gating function. Therefore, all commutation and associated control must be performed at ground transmit and receive end stations. This limits the flexibility of the system since the intelligence of the system is concentrated in the ground end stations. CDMA is also used in satellite applications but the previous lack
REF: 24499 processing on board satellite has avoided the invention of hybrid systems that use different types of air interfaces for the uplink and the downlink. Traffic in systems such as voice / multimedia tends to be of a triggered nature; a circumstance not favorable to TDMA and FDMA transmission modes. The use of a TDMA and FMDA transmission mode is unsatisfactory because the allocation of time slots and / or frequency channels requires a configuration time that is unacceptable in many applications. Also, changing the slot / frequency assignment to meet transient demands is a complex process that results in complex system control. COMPENDIUM OF THE INVENTION A satellite communications system, in accordance with the invention, provides a unique combination of CDMA, air-to-air interface, transmission and packet switching (i.e. asynchronous transfer mode) on board the satellite and downlink transmission TDM as described in the claims. In systems with burst or triggered traffic, packet switching is particularly advantageous due to its asynchronous nature to accept signals. Variations in arrival of signals are easily achieved. CDMA in packets is an efficient way to transmit traffic in bursts from different sites using a wireless channel. The capacity of a CDMA system generally depends on the interference caused by other users. If the traffic is in bursts and only packets are sent when there is information to be transmitted, the interference caused to other users is minimized and the number of users that the system can support increases. They also have the advantage that, beyond the initial configuration of the circuit, no additional configuration or signaling time is required to implement a burst of data and / or changes in data rate for a subscriber thus providing bandwidth capabilities. before demand. In a CDMA system, dispersion codes need to be assigned to individual users who wish to transmit information. The availability of dispersion codes and typical implementations in fact vastly exceeds the capacity of the air interface to carry specific numbers of simultaneous channels. The use of CDMA advantageously allows active channels that exceed the capacity to degrade elegantly as the use of the system is exceeded. One of the biggest limitations in the design of a satellite system is the energy available in the satellite. Multi-carrier systems such as CDMA require operating at low efficiency levels in order to avoid intermodulation distortion, making these systems inefficient in energy. By utilizing time division (ie, TDM) aggregation in the downlink, the system becomes more energy efficient while maintaining the multiple access benefits of CDMA. In a particular embodiment of the invention, ATM packets in a CDMA uplink signal include user data, which are processed and switched on board a satellite by ATM switching included within the satellite before its downlink supply. The ATM switch directs ATM packets to an appropriate one of the various output downlink beams, based on division information included in the pack header. Downlink signal is transmitted by multiplex processing with time division (ie TDM). It should be noted that the downlink can also use either frequency splitting (FDM) or code division (ie CDM). This invention has the advantage that no additional configuration time is required by the network, before a data rate change over a data burst. BRIEF DESCRIPTION DB THE DRAWINGS Figure 1 is a schematic of a satellite communication system;
Figure 2 is a block diagram of a circuit mode for uplink, satellite demodulation and commutation, and satellite downlink processing circuits. r > • OTATTA • An illustrative satellite communication system that couples a transmitting user's ground station to a receiving user's ground station is illustrated schematically in Figure 1. The satellite has multiple point beams to transmit and receive. Any user in any beam can communicate with any other user in the same or different beam. While individual transmit and receive stations 101 and 102 are illustratively shown respectively, the stations may be transmission points and reception points simultaneously of a communication system. These stations can already be fixed spatially / geographically or mobile, although in this specific modality, they are illustrated fixed on land while they are communicated. In addition, the stations can be bidirectional transceivers. They are only illustrated by unidirectional simplicity. The stations 101-1 include a satellite dish antenna 103, which directs an RF, CDMA signal in packets to a satellite 105. Once the link is established between the satellite 105 to the ground station 101-1, which includes code synchronization, the transmitter at station 101-1 will only send RF signals when there is an information packet to be transmitted or when it requires sending a packet to maintain synchronization. The station 102-1 receives a TDM RF signal containing packet information from the satellite 105 via its accompanying satellite pass antenna 104. Each beam includes a plurality of frequency bands. As illustrated, the satellite receives CDMA RF beam signals from other 101-N transmission stations and transmits TDM RF signals to a plurality of 102-M receiving stations. The uplink represents a synchronous CDMA system where all user signals arrive at the satellite with chip synchronization in order to minimize interference. The receiving satellite transceiver equipment receives a plurality of CDMA point beams at the receiving amplifiers 201-1 through 201-N. After processing in volumetric downconverters 202-1 to 202-N, the received signal is applied to a down-converter in volume followed by a multi-channel CDMA demodulator 203-1 which samples separates and demodulates the CDMA signal. The signals are processed in I and Q components and their dispersion is undone with discrete (digital) time techniques. Each CDMA channel contains a mix of M-PSK data signals at a variety of data rates. The signals received from all the beams are applied to the ATM switch 250. Outbound (ie, downlink in TDM format) transmission, from the ATM switch 250 is applied to TDM modulators 301-1 to 301-M including circuits for framing and forward error correction (FEC). The signals are converted in ascending form in blocks 302-1 to
302-M. Signals are amplified in 303-1 to 303-M modules using traveling wave tube amplifiers (TWTA) or solid-state power amplifiers (SSPA) that apply each channel to output bandpass filters in the same modules to suppress harmonics. These outputs are combined in beams at node 304-1 for downlink transmission. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following: